In MEMS capacitive acceleration sensors, angular velocity sensors, angle sensors, and the like, a CV conversion amplifier that converts a change ΔC in a capacitance value generated in an MEMS capacitive element into a voltage signal ΔV is used. It is necessary for the CV conversion amplifier to make a capacitance-voltage conversion gain ΔV/ΔC as large as possible in to relieve a noise specification of a circuit block at a subsequent stage.
However, in the past, if the capacitance-voltage conversion gain is increased, there is a problem in that an amplitude range of an output voltage of the CV conversion amplifier is remarkably decreased. The reason is that in the case of a pseudo differential CV conversion amplifier in which two single-ended operational amplifiers are used in parallel, if the capacitance-voltage conversion gain is increased, a center voltage level of an output of each single-ended operational amplifier considerably deviates from a desired value (usually, about ½ of a power voltage).
Further, in the case of a fully differential CV conversion amplifier in which one fully differential operational amplifier is used, if the capacitance-voltage conversion gain is increased, a common mode voltage of an input of the fully differential operational amplifier considerably deviates from a desired value. If the amplitude range of the output voltage of the CV conversion amplifier is decreased, an input signal allowable range of a sensor is narrowed. For example, in the case of an acceleration sensor, a range of an input acceleration signal which is normally detectable is narrowed.
In this regard, in the past, the output amplitude range of the CV conversion amplifier is secured such that a signal of a high voltage level among differential output signals of the CV conversion amplifier is determined by an OR circuit, held in a peak hold circuit, and a voltage for adjusting the center voltage level of the output is continuously generated. Further, when a setting of an adjustment voltage is stored as a digital value in advance, it is possible to select a suitable parameter in accordance with characteristics of a capacitive sensor. A configuration to which such a common mode voltage adjustment analog circuit is added is described in, for example, Patent Document 1.